Under steady state,the temperature of a body

The temperature gradient in a rod of length $75 \ cm$ is $40^{\circ} C/m$. If the temperature of the cooler end of the rod is $10^{\circ} C$,then the temperature of the hotter end is: (in $^{\circ} C$)

When the two ends of a metal rod are maintained at different temperatures and after some time every point of the rod attains a constant temperature,then:

Assertion: $A$ thermos bottle consists of a double-walled glass vessel with the space between the two walls evacuated, so that the heat transfer between the contents of the bottle and the outside is minimized.
Reason: The vacuum between the two walls inhibits the heat transfer by the radiation mechanism.
Which of the following is correct?

Four rods of silver,copper,brass,and wood are of the same shape. They are heated together after wrapping a paper on each. The paper will burn first on:

For water at $0^{\circ} C$,it takes one hour for the first $3 \ mm$ of ice layer formation. How many hours will it take for the next $6 \ mm$ of ice formation?